• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.12C
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• pp.1131-1137
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• 2009

In this paper, a resource management technique for digital duplexing (DD) systems using orthogonal frequency division multiple access (OFDMA) is proposed. The proposed technique can reduce the dynamic range of the signal received at the subscriber station (SS) and minimize the effects of inter-symbol interference (ISI) and inter-carrier interference (ICI) due to the time difference of arrival (TDoA) without using a cyclic suffix. It is shown by computer simulation that the proposed technique can reduce the number of bits for an analog-to-digital converter (ADC) and increase the signal-to-interference and noise ratio (SINR) significantly.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.3
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• pp.87-101
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• 1990

The purpose of this study is to estimate the flood discharge and runoff volume at a stream by using geomorphologic parameters obtained from the topographic maps following the law of stream classification and ordering by Horton and Strahier. The present model is modified from Cheng' s model which derives the geomorphologic instantaneous unit hydrograph. The present model uses the results of Laplace transformation and convolution intergral of probability density function of the travel time at each state. The stream flow velocity parameters are determined as a function of the rainfall intensity, and the effective rainfall is calculated by the SCS method. The total direct runoff volume until the time to peak is estimated by assuming a triangular hydrograph. The model is used to estimate the time to peak, the flood discharge, and the direct runoff at Andong, Imha. Geomchon, and Sunsan basin in the Nakdong River system. The results of the model application are as follows : 1.For each basin, as the rainfall intensity doubles form 1 mm/h to 2 mm/h with the same rainfall duration of 1 hour, the hydrographs show that the runoff volume doubles while the duration of the base flow and the time to peak are the same. This aggrees with the theory of the unit hydrograph. 2.Comparisions of the model predicted and observed values show that small relative errors of 0.44-7.4% of the flood discharge, and 1 hour difference in time to peak except the Geomchon basin which shows 10.32% and 2 hours respectively. 3.When the rainfall intensity is small, the error of flood discharge estimated by using this model is relatively large. The reason of this might be because of introducing the flood velocity concept in the stream flow velocity. 4.Total direct runoff volume until the time to peak estimated by using this model has small relative error comparing with the observed data. 5.The sensitivity analysis of velocity parameters to flood discharge shows that the flood discharge is sensitive to the velocity coefficient while it is insensitive to the ratio of arrival time of moving portion to that of storage portion of a stream and to the ratio of arrival time of stream to that of overland flow.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.69-74
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• 2016

A technique for improving estimation accuracy is introduced in order to locate the impact position of artillery shell during the weapon scoring test. Study on localization of impacts using acoustic measurement has been conducted and the usability of sensor array is verified with experiments. When the blast occurs above the ground in the firing range, the acoustic sensor above the ground can measure the directly propagated sound with the ground-reflected one. In this study, a method for reducing estimation error by using the reflection signal measurements based on the time difference of arrival method. Considering the reflection sound works as same as placing a virtual sensor symmetrically through the ground. This idea enables a virtual three-dimensional array configuration with a two-dimensional plane array above the ground as such. The time difference between the direct and the reflected propagations can be estimated using cepstrum analysis. Performance test has been made in the simulation experiment in the football size area.

• The Journal of the Korea Contents Association
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• v.14 no.3
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• pp.33-39
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• 2014

Domestic and international researches, about intelligent systems based on a variety of location recognitions using location information, have actively proceeded. The representative location recognition method based on PTMP(Point To Multi Point) communication uses TOA(Time Of Arrival) to calculate distances to a fixed node that you want to recognize a position. The method is used to obtain the fixed node location information from three nodes location information that is applied by the triangulation method. There are disadvantages, an infrastructure should be established at a specific space and the system established cost is needed, in the location recognition method based on the PTMP communication, In this paper, the ranging based PTP(Point To Point) location recognition method is proposed to revise the disadvantage of PTMP location recognition method. And then it is compared with PTMP communication location recognition to evaluate performance. In this way, PTMP and PTP communication location recognition systems based on ranging were constructed and tested in an indoor environment. Experiment results show that the proposed PTP location recognition method could be confirmed to improve accuracy more than 3 times when it was compared with the existed PTMP location recognition method.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.3
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• pp.201-207
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• 2008

This paper presents the implementation of a Tiling System about Preprocessing functions of JPEG 2000. The system covers the JPEG 2000 standard and is designed to determine the size of the image, to expand the image area and to split input image into several tiles. In order to split the input image with the progressive transmission into several tiles and transmit a tile of this image to others, this system store this image into Frame Memory. Therefore, this is designed as the Finite State Machine (FSM) to sequence through specific patterns of states in a predetermined sequential manner by using Verilog-HDL and be designed to handle a maximum 5M image. Moreover, for identifying image size for expansion, we propose several formula which are based on remainder after division (rem). we propose the true table which determines the size of the image input patterns by using results of these formula. Under the condition of TSMC 0.25um ASIC library, gate count is 18,725 and maximum data arrival time is 18.94 [ns].

• Journal of information and communication convergence engineering
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• v.10 no.4
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• pp.396-404
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• 2012

This paper proposes an analysis method to check the schedulability of a set of sporadic tasks under earliest deadline first (EDF) scheduler. The sporadic task model consists of subtasks with precedence constraints, arbitrary arrival times and deadlines. In order to determine the schedulability, we present an approach to find exact worst case response time (WCRT) of subtatsks. With the technique presented in this paper, we exploit the precedence relations between subtasks in an accurate way while taking advantage of the deadline of different subtasks. Another nice feature of our approach is that it avoids calculation time overhead by exploiting the concept of deadline busy period. Experimental results show that this consideration leads to a significant improvement compared with existing work.

• Journal of Korean Institute of Industrial Engineers
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• v.36 no.2
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• pp.138-145
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• 2010

In this paper, we consider the information processing system, which organizes the collected data to meaningful information when the number of data collected from multiple sources reaches to a predetermined number, and performs any action by processing the collected data, or transmits to other devices or systems. We derive an analytical model to calculate the time until it takes to process information after starting to collect data. Therefore, in order to complete the processing data within certain time constraints, we develop some design criteria to control various parameters of the information processing system. Also, we analyze the discrete time model for packet switching networks considering data with no particular arrival nor drop pattern. We analyze the relationship between the number of required packets and average information processing time through numerical examples. By this, we show that the proposed model is able to design the system to be suitable for user's requirements being complementary the quality of information and the information processing time in the system with time constraints.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.6
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• pp.611-619
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• 2016

Success in modern war depends on electronic warfare. Therefore, It is very important to identify the kind of Radar PRI modulations in a lot of Radar electromagnetic waves. In this paper, I propose an algorithm to identify Linear up Sliding PRI, Non-Linear up Sliding PRI and Linear Down Sliding PRI, Non-Linear Down Sliding PRI among many Radar pulses. We applied not only the TDOA(Time Difference Of Arrival) concept of Radar pulse signals incoming to antennas but also a rising and falling curve characteristics of those PRI's. After making a program by such algorithm, we input each 40 data to those PRI's identification programs and as a result, those programs fully processed the data in according to expectations. In the future, those programs can be applied to the ESM, ELINT system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.1
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• pp.131-138
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• 2000

This paper works on development of an algorithm for mapping of cerebral perfusion parameters using the gamma-variate curve fitting. The signal intensity variate curve according to time measured in each pixel of perfusion MRI is nonlinear, and various hemodynamic parameters are not computed accurately. Levenberg-Marquardt algorithm(LMA), nonlinear optimum algorithm with high convergent speed and stability, is used to compute them. That is, the signal intensity variate curve is fitted by the gamma-variate function. Various hemodynamic parameters - Cerebral Blood Volume(C.B.V), Mean Transit Time(M.T.T), Cerebral Blood Flow(C.B.F), Time-to-Peak(T.T.P), Bolus Arrival Time(B.A.T), Maximum Slope(M.S) - are computed using LMA.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.8
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• pp.1789-1798
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• 2012

IEEE 802.15.4a standard can provide a variety of location-based services for ZigBee or wireless network applications by adapting the time-of-arrival (TOA) ranging technique. The non-line-of-sight (NLOS) condition is the critical problem in the IEEE 802.15.4a networks, and it can significantly degrade the performance of the TOA-based localization. To enhance the location accuracy due to the NLOS problem, this paper proposes an energy-efficient low complexity localization algorithm. The proposed approach performs the ranging with the multicast method, which can reduce the message overhead due to packet exchanges. By limiting the search region for the location of the node, the proposed approach can enhance the location accuracy. Experimental results show that the proposed algorithm outperforms previous algorithms in terms of the energy consumption and the localization accuracy.